A part of the action of a firearm that throws the empty cartridge clear of the weapon. Single action revolvers usually have an ejector/extractor rod that is used to push the cartridge back through the loading port. Double action revolvers usually have a star built into the end of the chamber that ejects/extracts all cartridges at the same time.

On breech loading small arms, a device that removes the empty cartridge case after firing. Various methods have been devised to perform this function. On hinge frame guns the ejector is a spring attached to the extractor that causes a violent rearward snap of the extractor when the barrel is positioned to permit the cartridge to be thrown clear of the weapon. More often the ejector is a small protuberance within the receiver against which the case, having been extracted, strikes and is thrown clear. On hand ejector weapons, manual pressure on the extractor moves the cartridge case rearward to clear the chamber. In certain rifles, like the Garand, the ejector occurs in the bolt face as a spring loaded pin constantly exerting pressure on the case head. Opening the action allows instant ejection. In certain automatic pistols and foreign weapons the cartridge is ejected by the striker pin acting near the close of the rearward stroke of the firing cycle.

Most steam engines used for passenger and mainline work generally, had vacuum brakes. The vacuum was created by blowing steam through a series of cones. The larger cone (large ejector) was used to create the vacuum before the locomotive/train could move. A smaller ejector could be used to maintain the vacuum while running.